1. Field of the Invention
The present invention relates to an apparatus and a method for mounting an electronic part onto a circuit substrate. More particularly, the invention relates to a mounting apparatus and a mounting method which are suitably used when IC chips called flip chips each including bumps (projection type electrodes) are mounted onto a circuit substrate.
2. Related Background Art
In recent years, as electronic apparatuses have been miniaturized, it has been required to mount electronic parts onto a circuit substrate more densely. For the purpose of meeting such a requirement, there has been advanced promotion of the decreasing of pitches of parts as well as promotion of the increasing of positional accuracy during the mounting. In addition, as a new form, a technique in which an electronic part is mounted in a cavity defined within a multi-layered substrate has been frequently adopted.
In such a process for mounting an electronic part, conventionally, an image processing technique has been used as a method of enhancing the positional accuracy when an electronic part is mounted onto a circuit substrate. More specifically, a picture which is obtained by capturing an image of a circuit substrate with a camera or the like in advance is image-processed to thereby determine a position where an electronic part is intended to be mounted. At the same time, a position where an electronic part arranged in a loading position is to be arranged is also determined through the similar processing. Then, these positions are compared with each other to obtain relative positional displacements. The electronic parts arranged in the loading position are individually picked up with a pick-up nozzle to be temporarily placed on an intermediate stage. Then, the electronic parts are individually held by a mounting nozzle. Then, the processing for mounting the electronic parts are executed using the mounting nozzle after taking the positional displacements into consideration.
In a case where a chip such as an IC is mounted onto a circuit substrate, a mounting head holding a chip makes the chip come into contact with a predetermined position on the circuit substrate. Then, ultrasonic vibrations are applied to the chip concerned through the mounting head to connect (join) the chip to the circuit substrate. As the promotion of narrow pitches has been advanced as described above, it is required for the mounting nozzle as well not to interfere with a space in the periphery of the positions where the chips are to be mounted. Consequently, it is preferable that the shape of a chip holding portion in the mounting nozzle is fitted for the shape of a chip, and the size of the chip holding portion is smaller than that of the chip.
Moreover, even when the chip holding portion is smaller in size than the chip and its shape is fitted for the chip shape, it is conceivable that the pick-up nozzle cannot properly receive a chip from the part loading position. For example, it is supposed that as shown in FIG. 4A, the pick-up nozzle holds a chip in a state in which a central position of the pick-up nozzle is displaced by ΔX and ΔY in X-axis and Y-axis directions with respect to the center of the chip, and also a central axis of the pick-up nozzle is displaced by an angle Δθ with respect to a central axis of the chip. When paying attention to only a positional relationship between the chip and the circuit substrate as in the prior art, there is a big chance that these positional displacements are held even when the chip is delivered from the pick-up nozzle to a mounting nozzle (a suction nozzle for mounting).
If the chip is intended to be mounted in this state, when a space between the chip intended to be mounted and adjacent electronic parts is narrow, there is a possibility that an end portion of the mounting nozzle interferes with and comes into contact with these electronic parts. Moreover, as a style recently adopted style for mounting, there is a case where a chip is mounted onto a circuit substrate so as to be fitted into a cavity defined within the circuit substrate. In this case, however, there is a possibility that an end portion of the nozzle is projected from an end portion of a chip to thereby disable the fitting work itself. In addition, when a chip is joined to a circuit substrate using an ultrasonic wave, there is also a possibility that a deviation or the like occurs in application of a weight to the chip, and this exerts a bad influence on the joining state. Such a positional displacement may be within the allowable level in a current chip size or a current mounting situation. However, such a positional displacement is desirably improved in terms of promotion of the increasing of narrower pitches or the like.